Pixel structure and method of manufacturing a pixel structure

ABSTRACT

A pixel structure and a method of manufacturing a pixel structure are provided. The pixel structure includes an active device, a gate insulation layer, a dielectric insulation layer, a capacitance electrode, a protection layer and a pixel electrode. The active device includes a gate, a semiconductor channel layer, a source and a drain. The dielectric insulation layer covers the semiconductor channel layer. A dielectric index of the dielectric insulation layer is greater than a dielectric index of the gate insulation layer. The capacitance electrode is overlapped with the drain. The capacitance electrode, the drain and the dielectric insulation layer between the two constitute a storage capacitor structure. The protection layer is disposed on the dielectric insulation layer and the capacitance electrode is located between the protection layer and the dielectric insulation layer. The pixel electrode is disposed on the protection layer and connected to the drain of the active device.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan applicationserial no. 101125365, filed on Jul. 13, 2012. The entirety of theabove-mentioned patent application is hereby incorporated by referenceherein and made a part of this specification.

BACKGROUND OF THE INVENTION:

Field of the Invention

The present invention relates to a pixel structure and a manufacturingmethod thereof, and particularly, the invention relates to a pixelstructure having a high aperture ratio and a manufacturing methodthereof.

Description of Related Art

Currently, conventional flat-panel displays have pixel structures toconstitute minimum basic elements needed for displaying images, whereineach pixel structure generally includes an active device and a pixelelectrode. Generally, when the active devices in specific pixelstructures are activated via corresponding scanning lines, operatingvoltages provided by data lines are inputted to the pixel electrodes viathe activated active devices so as to display the corresponding displaydata. In addition, the pixel structure further includes a storagecapacitor such that the pixel structure has a function of maintainingvoltages. In other words, the storage capacitor is utilized to store theoperating voltage inputted to the pixel electrode via the active deviceso as to maintain the stability of the display image displayed by thepixel structure.

The storage capacitor is, generally, constituted of capacitanceelectrodes formed by metal patterns in the pixel structure. In order toincrease the capacitance of the storage capacitor for reaching goodstability of the display image, an area of capacitance electrodesoverlapping with each other is usually enlarged. However, such a designindicates that the disposition area of the metal pattern has to beenlarged and a display aperture ratio of the pixel structure is thusdecreased.

SUMMARY OF THE INVENTION

The invention provides a pixel structure having a desirable displayaperture ratio and sufficient storage capacitance.

The invention provides a method of manufacturing a pixel structureutilizing an insulation layer having a high dielectric index as adielectric layer of a storage capacitor, and allowing the storagecapacitor structure to be capable of providing sufficient storagecapacitance without occupying large layout area so as to enhance adisplay aperture ratio.

The invention provides a pixel structure disposed on a substrate. Thepixel structure includes an active device, a gate insulation layer, adielectric insulation layer, a capacitance electrode, a protection layerand a pixel electrode. The active device disposed on the substrateincludes a gate, a semiconductor channel layer, a source and a drain.The source and the drain are disposed above the gate and separated by agap such that the gate has at least a portion that is not overlappedwith the source and the drain, and the semiconductor channel layer is atleast disposed in the gap between the source and the drain. The gateinsulation layer is disposed between the gate and the semiconductorchannel layer, and the source and the drain are disposed between thegate insulation layer and the semiconductor channel layer. Thedielectric insulation layer is disposed above the substrate and coversthe semiconductor channel layer, wherein a dielectric index of thedielectric insulation layer is great than a dielectric index of the gateinsulation layer. The capacitance electrode is disposed above thedielectric insulation layer and the capacitance electrode is overlappedwith the drain such that the capacitance electrode, the drain and thedielectric insulation layer sandwiched between the two constitute astorage capacitor structure. The protection layer is disposed above thedielectric insulation layer and the capacitance electrode is disposedbetween the protection layer and the dielectric insulation layer. Thepixel electrode is disposed above the protection layer and connected tothe drain of the active device.

In an embodiment of the invention, the dielectric index of thedielectric insulation layer ranges from 5 to 10.

In an embodiment of the invention, a material of the dielectricinsulation layer includes aluminum oxide (Al₂O₃) or titanium dioxide(TiO₂).

In an embodiment of the invention, a film thickness of the dielectricinsulation layer ranges from 100 Å to 800 Å.

In an embodiment of the invention, the dielectric insulation layer has afirst contact opening exposing the drain and the protection layer has asecond contact opening communicated with the first contact opening suchthat the pixel electrode is connected to the drain via the first contactopening and the second contact opening communicated with each other.

In an embodiment of the invention, a material of the semiconductorchannel layer includes an oxide semiconductor material. The oxidesemiconductor material comprises Indium-Gallium-Zinc Oxide (IGZO), ZincOxide (ZnO), Stannic Oxide (SnO), Indium-Zinc Oxide (IZO), Gallium-ZincOxide (GZO), Zinc-Tin Oxide (ZTO) or Indium-Tin Oxide (ITO). The pixelstructure further includes a channel protection layer disposed on a topsurface of the semiconductor channel layer. A material of the channelprotection layer includes Indium-Gallium-Zinc Oxynitride (IGZON), ZincOxynitride (ZnON), Stannic Oxynitride (SnON), Indium-Zinc Oxynitride(IZON), Gallium-Zinc Oxynitride (GZON), Zinc-Tin Oxynitride (ZTON) orIndium-Tin Oxynitride (ITON).

The invention further provides a method of manufacturing a pixelstructure including the following steps: forming a gate above asubstrate; forming a gate insulating layer on the substrate to cover thegate; forming a source and a drain above the gate insulation layer,wherein the source and the drain above the gate are separated by a gapsuch that the gate has at least one portion that is not overlapped withthe source and the drain; forming a semiconductor channel layer abovethe source and the drain and the semiconductor channel layer is at leastdisposed in the gap; forming a dielectric insulation layer above thesubstrate to cover the source, the drain and the semiconductor channellayer, wherein a dielectric index of the dielectric insulation layer isgreat than a dielectric index of the gate insulation layer; forming acapacitance electrode above the dielectric insulation layer, wherein thecapacitance electrode is overlapped with the drain such that thecapacitance electrode, the drain and the dielectric insulation layersandwiched between the two constitute a storage capacitor structure;forming a protection layer above the dielectric insulation layer tocover the capacitance electrode; and forming a pixel electrode on theprotection layer and connected to the drain.

In an embodiment of the invention, the step of forming the source andthe drain, the step of forming the dielectric insulation layer and thestep of forming the capacitance electrode are processed sequentially.

In an embodiment of the invention, a material of the dielectricinsulation layer includes silicon oxide or titanium dioxide.

In an embodiment of the invention, the dielectric index of thedielectric insulation layer ranges from 5 to 10.

In an embodiment of the invention, the step of forming the semiconductorchannel layer is processed after the source and the drain are formed.

In an embodiment of the invention, a material of the semiconductorchannel layer includes an oxide semiconductor material. A step offorming a channel protection layer on a top surface of the semiconductorchannel layer is further included. The step of forming the channelprotection layer includes performing a nitridation process to thesemiconductor channel layer in a chamber for depositing the oxidesemiconductor material as the semiconductor channel layer. The oxidesemiconductor material includes Indium-Gallium-Zinc Oxide (IGZO), ZincOxide (ZnO), Stannic Oxide (SnO), Indium-Zinc Oxide (IZO), Gallium-ZincOxide (GZO), Zinc-Tin Oxide (ZTO) or Indium-Tin Oxide (ITO). Inaddition, a material of the channel protection layer includesIndium-Gallium-Zinc Oxynitride (IGZON), Zinc Oxynitride (ZnON), StannicOxynitride (SnON), Indium-Zinc Oxynitride (IZON), Gallium-ZincOxynitride (GZON), Zinc-Tin Oxynitride (ZTON) or Indium-Tin OxideNitride (ITON).

In an embodiment of the invention, a method of manufacturing the pixelstructure further includes forming a first contact opening exposing thedrain above the dielectric insulation layer and forming a second contactopening communicated with the first contact opening above the protectionlayer such that the pixel electrode manufactured subsequently isconnected to the drain via the first contact opening and the secondcontact opening communicated with each other.

In view of the foregoing, in the invention, the drain in the pixelstructure is disposed between the gate and the capacitance electrode,and a dielectric index of the dielectric insulation layer between thecapacitance electrode and the drain is greater than a dielectric indexof the gate insulation layer between the gate and the drain. Therefore,it is not required to have the capacitance electrode with large area forthe pixel structure in the invention to obtain sufficient storagecapacitance and helps to increase a display aperture ratio of the pixelstructure.

In order to make the aforementioned features and advantages of theinvention more comprehensible, embodiments accompanying figures aredescribed in details below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A to FIG. 6A illustrate schematic top views of componentsmanufactured in each step in a method of manufacturing a pixel structureaccording to an embodiment of the invention.

FIG. 1B to FIG. 6B are schematic cross-sectional views taken along asection line I-I′ of FIG. 1A to FIG. 6A, respectively.

DESCRIPTION OF EMBODIMENTS

FIG. 1A to FIG. 6A illustrate schematic top views of componentsmanufactured in each step in a method of manufacturing a pixel structureaccording an embodiment of the invention and FIG. 1B to FIG. 6B areschematic cross-sectional views taken along a section line I-I′ of FIG.1A to FIG. 6A, respectively. Referring to FIG. 1A and FIG. 1B first, amethod of manufacturing a pixel structure according to an embodiment ofthe invention includes forming a patterned conductive layer 110 on asubstrate 10 to define a gate 112 and a scanning line 114 where the gate112 connected thereto. Specifically, the gate 112 and the scanning line114 are constructed by a successive pattern of the patterned conductivelayer 110 and therefore the gate 112 can be regarded as one portion ofthe scanning line 114. However, in other embodiments, the patternedconductive layer 110 can include a linear pattern having a substantiallyfixed line width and a branch pattern connected to the linear pattern,wherein the scanning line 114 can be constituted of the linear patternhaving the fixed line width and the gate 112 can be constituted of thebranch pattern.

A material of the patterned conductive layer 110 can be a metal materialor other conductive materials. Herewith, a method of manufacturing thepatterned conductive layer 110 can include forming a conductive materiallayer (not shown) on the substrate 10 and then patterning the conductivematerial layer (not shown) to constitute the patterned conductive layer110, in which the step of patterning can include lithography and etchingprocesses, but is not limited thereto. For the time being, the step offorming the patterned conductive layer 110 can use a mask. In anotherembodiment, a method of manufacturing the patterned conductive layer 110can include forming a conductive material on a partial area of thesubstrate 10 through a printing process to constitute the patternedconductive layer 110.

Next, referring to FIG. 2A and FIG. 2B, a gate insulation layer 120covering the patterned conductive layer 110 is formed on the substrate10 and another patterned conductive layer 130 is formed on the gateinsulation layer 120. Herewith, a material of the gate insulation layer120 includes an insulation material such as silicon oxide, siliconnitride and the like, and a material of the patterned conductive layer130 can include a metallic material or non-metallic conductive material,such as metallic oxide conductive material or the like. A method ofmanufacturing the patterned conductive layer 130 can include forming aconductive material layer (not shown) on the substrate 10 and thenpatterning the conductive material layer (not shown) to constitute thepatterned conductive layer 130, wherein the step of patterning caninclude lithography and etching processes. In other words, the step offorming the patterned conductive layer 130 according to the presentembodiment can use another mask.

The patterned conductive layer 130 includes a data line 132, a source134 and a drain 136. The source 134 and the drain 136 above the gate 112are separated from each other by a gap D and partially overlapped withthe gate 112 such that the gate 112 has at least a portion that is notoverlapped with the source 134 and the drain 136. In other words, thegap D is substantially located above the gate 112 in a thicknessdirection such that the gate 112 in the gap D is not shielded by oroverlapped with the source 134 and the drain 136. According to thepresent embodiment, the source 134 can be one portion of the data line132, but the invention is not limited thereto. In other description ofembodiments, the source 134 can be constituted of a conductive patternconnected to the data line 132.

Then, referring to FIG. 3A and FIG. 3B at the same time, a semiconductorchannel layer 140 is formed on and partially overlapped with the source134 and the drain 136. The step of forming the semiconductor channellayer 140 can include forming a semiconductor material layer (not shown)on the substrate 10, and then patterning the semiconductor materiallayer (not shown) into the semiconductor channel layer 140. The step ofpatterning can include lithography and etching processes. In otherwords, the step of forming the semiconductor channel layer 140 can usefurther another mask.

Specifically, the semiconductor channel layer 140 is, for example, atleast disposed in the gap D configured between the source 134 and thedrain 136 such that the semiconductor channel layer 140 is connectedbetween the source 134 and the drain 136. In addition, the semiconductorchannel layer 140 substantially defines a location of the gate 112, thatis, a portion of the patterned conductive layer 110 overlapped with thesemiconductor channel layer 140 is the gate 112 and the rest portion ofthe patterned conductive layer 110 can be the scanning line 114. In thisway, an active device 102 is constituted of the gate 112, the source134, the drain 136 and the semiconductor channel layer 140 together.

In addition, the gate insulation layer 120 is disposed between the gate112 and the semiconductor channel layer 140, and the source 134 and thedrain 136 are disposed between the gate insulation layer 120 and thesemiconductor channel layer 140. It is known, from such a stackingstructure, that the active device 102 is a co-planar type thin filmtransistor (TFT). In other words, the step of forming the semiconductorchannel layer 140 is processed after the source 134 and the drain 136are formed. However, the invention is not limited thereto.

A material of the semiconductor channel layer 140 can be amorphoussilicon, polysilicon, organic semiconductor material or oxidesemiconductor material. In other words, any semiconductor material canbe chosen to form the semiconductor channel layer 140. If a material ofthe semiconductor channel layer 140 is oxide semiconductor material, aprotection layer 142 can be selectively disposed on a top surface of thesemiconductor channel layer 140. In other words, the protection layer142 can be disposed on a surface of the semiconductor channel layer 140away from the gate 112 such that the semiconductor channel layer 140 isdisposed between the protection layer 142 and the gate insulation layer120, and disposed between the protection layer 142 and the source 134and the drain 136 constituted by the patterned conductive layer 130.

It is to be noted that a method of forming the protection layer 142 canbe injecting nitrogen gas into the chamber for deposing the oxidesemiconductor material prior to the end of the deposition process of theoxide semiconductor material. As a result, the semiconductor channellayer 140 and the protection layer 142 contain the same metallicelement, and a material of the protection layer 142 is substantially anoxynitride semiconductor. Generally, an oxide semiconductor material forthe semiconductor channel layer 140 includes Indium-Gallium-Zinc Oxide(IGZO), Zinc Oxide (ZnO), Stannic Oxide (SnO), Indium-Zinc Oxide (IZO),Gallium-Zinc Oxide (GZO), Zinc-Tin Oxide (ZTO) or Indium-Tin Oxide(ITO). Therefore, a material of the protection layer 142 correspondinglyincludes Indium-Gallium-Zinc Oxynitride (IGZON), Zinc Oxynitride (ZnON),Stannic Oxynitride (SnON), Indium-Zinc Oxynitride (IZON), Gallium-ZincOxynitride (GZON), Zinc-Tin Oxynitride (ZTON) or Indium-Tin Oxynitride(ITON).

In the present embodiment, the oxynitride semiconductor and the oxidesemiconductor material can be formed in the same deposition chamberusing in-situ deposition procedures or successively depositionprocedures. Therefore, in the process of forming the oxynitridesemiconductor and the oxide semiconductor material on the substrate 10,the substrate 10 does not leave the deposition chamber. Therefore, theoxide semiconductor material is always covered by the oxynitridesemiconductor and is not exposed in an atmospheric environment. As aresult, the protection layer 142 constituted by oxynitride semiconductorcan provide suitable protection effect such that the semiconductorchannel layer 140 constituted by the oxide semiconductor material is notaffected by moisture and oxygen in the atmospheric environment and hasbetter electrical performance. However, a disposition and amanufacturing of the protection layer 142 are used only fordemonstration and illustration and are not intended to limit theinvention thereto. In other embodiments, when a material of thesemiconductor channel layer 140 is a material less likely be affected bymoisture such as polysilicon or amorphous silicon, the semiconductorchannel layer 140 does not need to be covered by the protection layer142.

Later, referring to FIG. 4A and FIG. 4B, a dielectric insulation layer150 is formed on the substrate 10 and a capacitance electrode 160 isformed on the dielectric insulation layer 150. The dielectric insulationlayer 150 is disposed on the substrate 10 and covers the active device102, and the capacitance electrode 160 is disposed on the dielectricinsulation layer 150. In addition, the capacitance electrode 160 isoverlapped with the drain 136 such that the capacitance electrode 160,the drain 136 and the dielectric insulation layer 150 sandwichedtherebetween constitute a storage capacitor structure 104. In presentembodiment, the step of forming the source 134 and the drain 136, thestep of forming the dielectric insulation layer 150 and the step offorming the capacitance electrode 160 are processed successively to formthe storage capacitor structure 104. In other words, the storagecapacitor structure 104 is constituted by the drain 136, the dielectricinsulation layer 150 and the capacitance electrode 160 in a way ofstacking upward successively from the substrate 10.

Herewith, a method of manufacturing the capacitance electrode 160 caninclude, first, forming a conductive material layer (not shown) on thedielectric insulation layer 150 and then patterning the conductivematerial layer(not shown) to constitute the capacitance electrode 160,wherein the step of patterning can include lithography and etchingprocesses. In other words, the step of forming the capacitance electrode160 can use again another mask. The capacitance electrode 160 is, forexample, manufactured by a conductive material such as metals and thecapacitance electrode 160 can cross the data line 132 and, for example,is disposed parallel to the scanning line 114. Overall, the presentembodiment, for example, utilizes three conductive layers to constitutethe active device 102 and the capacitor structure 104.

In addition, the step of forming the dielectric insulation layer 150 is,for example, performing a physical vapor deposition (PVD), and thedielectric insulation layer 150 can be manufactured by utilizing aninsulation material with higher dielectric index. For example, amaterial of the dielectric insulation layer 150 includes aluminum oxide,titanium oxide, or other metallic oxide material that can be utilized tomanufacture by the physical vapor deposition or the sputtering process,wherein aluminum oxide includes Al₂O₃ and titanium oxide includes TiO₂.

Take the present embodiment as an example, a material of the gateinsulation layer 120 is, for example, silicon oxide or silicon nitride,and a material of the dielectric insulation layer 150 includes aluminumoxide or titanium oxide. As a result, a dielectric index of thedielectric insulation layer 150 is greater than a dielectric index ofthe gate insulation layer 120, wherein the dielectric index of thedielectric insulation layer 150, for example, ranges from 5 to 10. Dueto that the dielectric index of the dielectric insulation layer 150 isgreater than the dielectric index of the gate insulation layer 120, afilm thickness of the dielectric insulation layer 150 rangesapproximately from 100 Å to 800 Å which is capable of providingsufficient dielectric properties. In comparison, it may has a filmthickness of 500 Å to 1500 Å for the gate insulation layer 120 to becapable of providing sufficient dielectric properties. Therefore, thefilm thickness of the dielectric insulation layer 150 of the presentembodiment can be thinner than the film thickness of the gate insulationlayer 120.

It is to be noticed that a material of the dielectric insulation layer150 of the present embodiment is aluminum oxide or titanium oxide. Adeposition rate of such a material is low and the material is notsuitable for manufacturing the gate insulation layer 120. Consequently,the present embodiment adopts materials with various dielectricproperties to manufacture respectively the gate insulation layer 120 andthe dielectric insulation layer 150 to avoid longer period of time formanufacturing the gate insulation layer 120 that affects overallmanufacture of the active device 102. Also, the dielectric insulationlayer 150 can be utilized to provide desirable dielectric properties soas to fulfill the needed storage capacitor structure 104. For example,the dielectric insulation layer 150 has high dielectric index and thinfilm thickness which help to increase capacitance per unit area of thestorage capacitor structure 104 and reduce a size of area of the storagecapacitor structure 104.

Next, referring to FIG. 5A and FIG. 5B, a protection layer 170 is formedon the dielectric insulation layer 150 such that the capacitanceelectrode 160 is sandwiched between the dielectric insulation layer 150and the protection layer 170. In addition, further in the presentembodiment, a first contact opening 152 is formed in the dielectricinsulation layer 150 and a second contact opening 172 is formed in theprotection layer 170. The drain 136 is exposed by the first contactopening 152 and the second contact opening 172 communicated with thefirst contact opening 152. Therefore, the drain 136 can be exposed byboth the first contact opening 152 and the second contact opening 172together.

Later, referring to FIG. 6A and FIG. 6B, a pixel electrode 106 is formedon the substrate 10. The pixel electrode 106 is connected to the drain136 via the first contact opening 152 and the second contact opening 172so as to form a pixel structure 100 disposed on the substrate 10.

Specifically, the pixel structure 100 includes the active device 102,the gate insulation layer 120, the dielectric insulation layer 150, thecapacitance electrode 160, the protection layer 170 and the pixelelectrode 106. The active device 102 includes the gate 112, thesemiconductor channel layer 140, the source 134 and the drain 136. Thepixel electrode 106 is disposed above the protection layer 170 andconnected to the drain 136 of the active device 102. The capacitanceelectrode 160 is disposed above the dielectric insulation layer 150 andthe capacitance electrode 160 is overlapped with the drain 136 such thatthe capacitance electrode 160, the drain 136 and the dielectricinsulation layer 150 sandwiched therebetween constitute the storagecapacitor structure 104. The protection layer 170 is disposed above thedielectric insulation layer 150, and the capacitance electrode 160 isdisposed between the protection layer 170 and the dielectric insulationlayer 150. In addition, the dielectric insulation layer 150 is disposedabove the substrate 10 and covers the semiconductor channel layer 140,the source 134 and the drain 136.

With regard to the active device 102, a gap D above the gate 112 isbetween the source 134 and the drain 136 such that the gate 112 has atleast one portion that is not overlapped with the source 134 and thedrain 136. Also, the semiconductor channel layer 140 at least isdisposed in the gap D to be connected between the source 134 and thedrain 136. The gate insulation layer 120 is disposed between the gate112 and the semiconductor channel layer 140, and the source 134 and thedrain 136 are disposed between the gate insulation layer 120 and thesemiconductor channel layer 140. Therefore, the active device 102 can bea coplanar thin film transistor (TFT).

In the present embodiment, a dielectric index of the dielectricinsulation layer 150 is greater than the dielectric index of the gateinsulation layer 120, wherein the dielectric index of the dielectricinsulation layer 150 ranges from 5 to 10. In addition, a film thicknessof the dielectric insulation layer 150 ranges from 100 Å to 800 Å. As aresult, the design of the present embodiment helps to obtain desirablecapacitance for the storage capacitor structure 104 and keeps a minimumlayout area, and increases a display aperture ratio for the pixelstructure 100.

Generally speaking, a capacitor structure is constituted of twoelectrodes and a middle layer sandwiched between two electrodes. Acapacitance of the capacitor structure is in direct proportion to anoverlapping area of two electrodes and is in reverse proportion to afilm thickness (distance between two electrodes) of the middle layer. Inaddition, the film thickness of the middle layer is related to adielectric index of a material used for the middle layer. For example,in order to obtain same dielectric properties, the middle layerconstituted by a high dielectric index material requires thinner filmthickness while the middle layer constituted by a low dielectric indexmaterial requires thicker film thickness. Therefore, the middle layerconstituted by materials with various dielectric indexes and sandwichedbetween two electrodes affects not only capacitance levels of thecapacitor structure but also an overlapping area needed for twoelectrodes.

For example, the dielectric index of aluminum oxide is approximately 7.According to the design of the present embodiment, when the middle layer(i.e. the dielectric insulation layer 150) constituted by a materialwith a higher dielectric index (i.e. aluminum oxide) and sandwichedbetween the capacitance electrode 160 and the drain 136, the dielectricinsulation layer 150 having a film thickness ranging approximately from500 Å to 750 Å can provide sufficient dielectric properties. At thistime, the storage capacitor structure 104 constituted by overlapping thecapacitance electrode 160 and the drain 136 has a capacitance per unitarea of approximately 1.239 fF/μm².

In a comparative example, the dielectric index of silicon oxide isapproximately 3.8. When a middle layer constituted by a material havinga lower dielectric index (i.e. silicon oxide) is sandwiched between twoelectrodes to form a storage capacitor structure, the middle layerhaving approximately 900 Å of a film thickness is capable of providingsufficient dielectric properties. At this time, the storage capacitorstructure constituted by two overlapping electrodes has a capacitanceper unit area of approximately 0.374 fF/μm².

According to the capacitance per unit area, in order to execute a designhaving the same capacitance, an overlapping area of two electrodes ofthe capacitor structure in the comparative example is required to beapproximately 3.313 times of the overlapping area of two electrodes, thecapacitance electrode 160 and the drain 136, of the capacitor structurein the present embodiment. In other words, in the present embodiment,utilizing a material having a high dielectric index to manufacture thedielectric insulation layer 150 for forming the storage capacitorstructure 104 helps to obtain desirable capacitance in a limited layoutarea, or helps to obtain the same capacitance in even smaller layoutarea. When the capacitance electrode 160 is manufactured with an opaquematerial (that is, the storage capacitance structure 104 is an opaquecomponent), the design of the present embodiment has little negativeimpact on a display aperture ratio because the storage capacitorstructure 104 requires smaller area.

In addition, the dielectric insulation layer 150 of the presentembodiment is manufactured with a material having a high density such asaluminum oxide which has not only high dielectric properties but alsofurther prevents semiconductor channel layer 140 from being damaged byexternal substances (such as moistures and the like). Therefore, in thepixel structure 100 of the present embodiment, when an oxidesemiconductor material is used to form the semiconductor channel layer140 disposed in the active device 102, the semiconductor channel layer140 is capable of providing desirable electrical properties and is lessprone to be damaged.

In summary, in the invention, a material having higher dielectric indexis used as the dielectric insulation layer of the storage capacitorstructure and helps to reduce the needed disposition area for thestorage capacitor structure and further increases a display apertureratio. Therefore, the pixel structure of the present embodimentaccording to the invention can obtain high display aperture ratio andsufficient storage capacitance.

Although the invention has been described with reference to the aboveembodiments, it is not intended to limit the invention thereto. It isapparent to people of the ordinary skill in the art that modificationsand variations to the described embodiments may be made withoutdeparting from the spirit and scope of the invention. Accordingly, thescope of the invention will be defined by the attached claims and not bythe above detailed descriptions.

What is claimed is:
 1. A pixel structure disposed on a substrate,comprising: an active device disposed on the substrate comprising agate, a semiconductor channel layer, a source and a drain, wherein thesource and the drain are disposed above the gate and separated by a gapsuch that the gate has at least one portion that is not overlapped withthe source and the drain, and the semiconductor channel layer is atleast disposed in the gap between the source and the drain; a gateinsulation layer disposed between the gate and the semiconductor channellayer, wherein the source and the drain are disposed between the gateinsulation layer and the semiconductor channel layer; a dielectricinsulation layer disposed on the substrate and covering thesemiconductor channel layer, wherein a dielectric index of thedielectric insulation layer is greater than a dielectric index of thegate insulation layer; a capacitance electrode disposed on thedielectric insulation layer and the capacitance electrode overlappingwith the drain such that the capacitance electrode, the drain and thedielectric insulation layer sandwiched between the capacitance electrodeand the drain constitute a storage capacitor structure, wherein thecapacitance electrode is not overlapping with the gate and the source; aprotection layer disposed on the dielectric insulation layer, whereinthe capacitance electrode located between the protection layer and thedielectric insulation layer; and a pixel electrode disposed on theprotection layer and connected to the drain of the active device.
 2. Thepixel structure as recited in claim 1, wherein the dielectric index ofthe dielectric insulation layer ranges from 5 to
 10. 3. The pixelstructure as recited in claim 1, wherein a material of the dielectricinsulation layer comprises aluminum oxide (Al₂O₃) or titanium dioxide(TiO₂).
 4. The pixel structure as recited in claim 1, wherein a filmthickness of the dielectric insulation layer ranges from 100 Å to 800 Å.5. The pixel structure as recited in claim 1, wherein the dielectricinsulation layer has a first contact opening exposing the drain and theprotection layer has a second contact opening communicated with thefirst contact opening such that the pixel electrode is connected to thedrain via the first contact opening and the second contact openingcommunicated with each other.
 6. The pixel structure as recited in claim1, wherein a material of the semiconductor channel layer comprises anoxide semiconductor material.
 7. The pixel structure as recited in claim6, wherein the oxide semiconductor material comprisesIndium-Gallium-Zinc Oxide (IGZO), Zinc Oxide (ZnO), Stannic Oxide (SnO),Indium-Zinc Oxide (IZO), Gallium-Zinc Oxide (GZO), Zinc-Tin Oxide (ZTO)or Indium-Tin Oxide (ITO).
 8. The pixel structure as recited in claim 7,further comprising a channel protection layer disposed on a top surfaceof the semiconductor channel layer.
 9. The pixel structure as recited inclaim 8, wherein a material of the channel protection layer comprisesIndium-Gallium-Zinc Oxynitride (IGZON), Zinc Oxynitride (ZnON), StannicOxynitride (SnON), Indium-Zinc Oxynitride (IZON), Gallium-ZincOxynitride (GZON), Zinc-Tin Oxynitride (ZTON) or Indium-Tin Oxynitride(ITON).